The codes used for the simulation of plasma turbulence base on fluid theory. Codes at different levels of complexity are available. They solve the continuity equations and equations of motion for the electron and the ion fluid. Differences appear in geometry on which the equations are solved, in effects taken into account for the parallel electron motion and in Larmor-radius effects. The turbulence codes used at IPF have been developed by collaboration partners.
The code output consists of the temporal evolution of density and potential fluctuations on a 2 or 3-dimensional spatial grid. This information is equivalent to the data measured with the probe arrays. The numerical data are used for direct comparisons with experiment and for testing complex data-analysis techniques.
The code developed by V. Naulin, Risoe, Denmark, solves the Hasegawa-Wakatani equations in slab geometry. The model is valid for drift-wave turbulence as also observed in the TJ-K plasma. Curvature effects are not part of this model. The code was used to test the bicoherence analysis of the turbulent cascade on a well defined physical basis.
The DALF3 code
The Drift- ALFvén code DALF3 solves the fluid equations in 3-dimensional flux-tube geometry. It was developed by B.D. Scott IPP, Garching. Due to the flux-tube geometry, DALF3 takes into account curvature effects which are important for toroidal plasmas. Furthermore, electron inertia and electromagnetic effects are taken into account in the parallel equation of motion. The model applies to turbulence in the edge of fusion plasmas and was used to study the transition from drift-wave to interchange turbulence.
The GEM3 code
The code GEM3 (Gyrofluid Electro Magnetic), also developed by B.D. Scott, is an extension of the DALF3 code. The model contains finite ion-temperature effects and self-consistently evolves the density profile. It is a state of the art fluid code for simulating plasma turbulence in edge and core of tokamak plasmas.
Head of Plasma Dynamics and Diagnostics / Library officer